Commentator: Many people argue that the release of chlorofluorocarbons into the atmosphere is harming humans by dam...

Antionetteon December 10, 2013

Help!

How do you diagram this question?
I think the commentator is weakening a cause/effect argument by showing cause with no effect but what about the last sentence?

4 Replies

Melodyon December 16, 2013

This argument does not contain sufficient and necessary sentences, so we cannot diagram it. You are correct to identify this as a cause and effect weaken argument. The commentator is trying to weaken the claim that "the release of chlorofluorocarbons into the atmosphere is harming humans by damaging the ozone layer, thus allowing increased amount of ultraviolet radiation to reach Earth." The claim states: damage to the ozone layer causes harm to humans. You are correct to point out that the commentator, in an attempt to weaken this cause and effect argument, is trying to show cause without effect, i.e. "300,000 years ago a supernova greatly damaged the ozone layer, with no significant effect on our earliest ancestors." Great work!

The commentator concludes that because "the supernova's disruption was much greater than the estimated effect of chlorofluorocarbons today, there is no reason to think that these chemicals in the atmosphere harm humans in this way."

Thus, answer choice (C) is the correct answer because, if true, it would most seriously weaken the commentator's argument. If it were true that our "earliest ancestors possessed genetic characteristics making them more resistant than we are to the harmful effects of ultraviolet radiation," then the commentator's "cause without effect" defense no longer holds. Our earliest ancestors possessed an extra protection against the ultraviolet radiation that we do not possess. Thus, though the damage to the ozone layer 300,000 years ago posed no significant effect on our earliest ancestors, that does not mean it wouldn't pose significant harm to us, since we do not have the genetic characteristics that made them more resistant to the radiation.

Hope that was helpful! Please let us know if you have any other questions.

(D) tells us that the ozone repairs itself slowly. However, the authorof the passage would be o.k. with accepting this because the authorclaims that additional amounts of UV light don't harm humans becausethere was no significant effect on our earliest ancestors when thesupernova damaged the ozone layer. Thus, (D) doesn't weaken theauthor's claim that increased amounts of UV radiation don't harmhumans.

(E) says, "Scientists have discovered that genetic changes occurred inour ancestors during the period in which the supernova affectedEarth."

The problem with (E) is that we don't know what these genetic changeswere and what caused them. It's possible that they had nothing to dowith the supernova. (E) is baiting us into thinking that correlationproves causation, and as we know, it doesn't. What if the geneticchanges were an increase in brain size, making our ancestors smarter?(E) is way too vague and doesn't weaken the author's argument.

Does this make sense? Let us know if you have any questions!

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